Light emitting diode dies typically emit light over a wide angle, e.g., up to 90 degrees off the center axis. It is common to redirect the light emitted by the LED using a lens or a reflective cup. Such simple optical techniques are adequate for devices used as indicator lights or where a precise emission pattern is not required.
Innovative optical solutions must be used, however, when the light output of an LED illumination system is narrowly specified for a system, including, for example, entendue limited systems, such as for projection displays (e.g., rear projection TVs or front projectors), automotive applications (e.g., headlights), fiber optics, accent lighting, color mixing in a compact space, and other applications.